Learn Turkish: Müdür, kâhyaya misafir için özel bir parti organize ettirtiyor. - The manager is having the butler have a special party organized for the guest.

The helper verb is etmek (used here in the compound verb organize etmek, to organize). First, we add the causative suffix -tir to get ettirmek (to have someone organize). Then, we add a second causative suffix -t to get the double causative ettirtmek (to have someone have someone else organize).

Who is actually organizing the party here?

Neither the manager nor the butler! The double causative ettirtiyor implies a chain of command: the manager (müdür) gives the order to the butler (kâhyaya), and the butler will instruct an unnamed third party (like the catering staff) to do the actual, physical organizing.

Why is kâhya (butler) in the dative case (kâhyaya)?

In causative sentences, the case of the person given the task depends on the verb. If the verb takes a direct object—like özel bir parti (a special party) does here—the person being made to do it must take the dative case (-e/-a). This rule prevents a sentence from having multiple competing direct objects.

Why does the first causative suffix start with a 't' in ettirmek instead of the usual -dir?